Ryanair announced on Friday that it would recognise pilot unions for the first time in its 32-year history in a bid to stop its first pilot strike from taking place later in the day.

Chief executive Michael O'Leary's refusal to recognise unions was at the heart of the ultra low-cost model he developed to turn a small Irish regional airline into Europe's largest carrier by passenger numbers.

"Recognising unions will be a significant change for Ryanair, but we have delivered radical change before," O'Leary said in a statement. "We hope and expect that these structures can and will be agreed with our pilots early in the New Year."

The move comes after pilots in several countries threatened strike action in the busy run-up to Christmas.

The Irish carrier said it would hold talks with unions in Ireland, Britain, Germany, Italy, Spain and Portugal to recognise them as long as they established a committee made up solely of Ryanair pilots, "as Ryanair will not engage with pilots who fly for competitor airlines in Ireland or elsewhere."

Pilots and ground crew in Italy were due to take action first with a four-hour strike later on Friday, to be followed by a 24-hour stoppage by pilots in Ireland and Portugal on December 20.

The pilots have mobilised in the wake of the announcement of 20,000 flight cancellations by the Irish carrier, which it blamed on a lack of standby pilots due to a failure in its rostering following a rule change by Irish regulators.

Ryanair had brought back Peter Bellew, previously the CEO of Malaysia Airlines and Ryanair's former director of flight operations, to help deal with the staffing issue.

The airline's chief people officer Eddie Wilson said there was no reason to think costs would increase as a result.